Release v2.11.2

Fixed

• A ring cure near its target kept re-proposing the triples it had just declined.
  Declining a ring that the closure ladder could not pull shut leaves its three groups
  unreacted, which is the point -- but the next search then offered the same groups,
  ran the same eight-stage ladder, and declined them again. htpolynet-study measured
  the cost on a 2.11.1 build: at conversion 0.97 with 24 groups left, nine iterations
  running produced 77 declines and not one ring, at about 67 s each.

  A declined combination is now passed over while any untried ring is within the search
  radius. It is a preference and not a prohibition: that cure escaped on iteration 41
  and finished at 0.971, because the relaxation between iterations moves the groups, so
  a triple that failed once can still close later. When the memory is the only thing
  left keeping an iteration idle, the search lifts it and offers those rings again
  rather than stand still.